The present invention relates to a method of and an arrangement for cooling a hot product gas with adhesive or fusible particles which lose their adhesiveness during cooling. More particularly, it relates to such a method and arrangement in accordance with which a ring-shaped jet of a cooling fluid is injected into the hot product gas in a cooling zone with a circular cross-section in a flow direction of the gas.
During cooling of hot product gases containing adhesive or fusible particles which lose their adhesiveness when they exceed a predetermined rigidifying temperature, there is a danger that these particles lead to deposits on the walls of the utilized apparatuses or respective installation parts due to baking. The effective growth of these deposits leads over time to the fact that the gas path in the utilized apparatuses gradually displaces and thereby the total installation becomes inoperative. A pronounced example for such a product gas which contains adhesive or fusible components is a partial oxidation gas recovered during the partial oxidation of coal and/or respective carbon carriers at temperatures above the slag melting point. The partial oxidation gas which leaves the gasifier with a temperature of 1200 to 1700.degree. C. contains adhesive or fusible slag particles and/or respective tar components which lead to the above described deposits. During cooling and further treatment of such a gas, suitable measures must be taken which do not affect the cooling and subsequent processing steps by deposits on the walls of the utilized apparatuses, on the heat exchange surfaces and/or in the pipes.
It is known in principle to inject or nozzle a ring-shaped jet of a cooling fluid in the flow direction of the gases into the heat product gas stream for cooling the hot product gas. Such an introduction leads to a truncated-cone-shaped formation of the ring-shaped jet having a converging primary part and diverging secondary part when it is superposed on the product gas stream. The examples for the practical utilization for this cooling principle with the supply of the cooling fluid through a ring-shaped gap in the hot product gas stream have been known for a long time. This process is used for example during a so-called rolling gas process, in which a so-called return gas is admixed to the hot combustion gas for the temperature adjustment. This is disclosed, for example, in Ullmann, Volume 1, 1951, page 182, FIG. 332. Also, a toroid air heater operates on the same principle, in accordance with which the cold air is admixed to the hot combustion gas in a mixing chamber. Recently this principle has been also used for cooling of hot product gas which contains adhesive or fusible particles, especially for cooling of partial oxidation gas. This is disclosed for example, in the German document DE-OS 3,524,802. Due to the introduction of the cooling fluid through a ring-shaped gap, the wall contact of the particles is avoided and thereby the danger of deposits is precluded. It has been however shown that this object has not been achieved in a satisfactory manner. The recirculation flow formed on the edges of the truncated-cone-shaped cooling fluid jet does not retain the adhesive particles away of the walls, but instead leads them to the walls.